This invention relates to throttling devices or fluid resistance devices as part of fluid systems where dissipation of moderate pressure differentials is desired. Such dissipation of energy should take place with a minimum of generated noise level.
Acoustical energy, i.e., Soundpower, increases roughly as the 18th power of the flow area of a valve orifice but only to the 10th power of increase in mass flow. It is therefore easy to see that important noise savings can be made simply by keeping the orifice diameter constant and by accommodating the increase in mass flow through increase in the number of parallel orifices. For example, about 14 dB can be saved with a 64-fold increase in mass flow when, instead of employing a single orifice 8 times enlarged in diameter, 64 individual orifices of the same original diameter are used.
While the concept of multiple orifice resistance trim is not new, the production of conventional state of the art devices is rather costly as it involves mechanically drilling a multitude of small holes into heavy sections of stainless plates (see U.S. Pat. No. 3,665,965).
My invention overcomes these difficulties by employing a stack of identical stampings which, when arranged in a certain circularly off-set pattern, automatically create an intricate network of individual small horizontal throttling passages from which fluid is allowed to expand into the downstream pipe cavity.
After suitable arrangement of the plates against each other, the stack is either mechanically fastened or simply brazed together and against a solid flange being part of a piping system.
Any solid or fluid medium vibrating in response to noise energy waves will convert a portion of the energy it receives to heat. With fluids it is the fluid viscosity which occasions the conversion, or damping. A similar noise energy damping reaction occurs as well in solids.
Further, the amount of energy passed on through such media varies with the negative power of the distance that the energy travels within the medium. And in solids like the metals found in pipes, the attenuation in the medium increases with the frequency of the noise energy.
It is thus an object of the present invention to provide apparatus for pressure reduction or throttling of fluid flow with a low acoustical efficiency.
It is a further object of the invention to provide an acoustical filter for absorbing downstream the noise of conventional valves and thereby preventing the radiation of that noise through the fluid conduit walls to its external surroundings.
It is a further object of the invention to provide a device for throttling fluid flow with greatly reduced noise generation by minimum fluid velocity constricting jet means.
It is a further object of the present invention to provide a fluid pressure throttling device which generates noise at a frequency which provides for greater attenuation of the noise energy by the fluid conduit.
A further object of my invention is to provide a pressure reducing device having means to adjustably select the number of flow passages exposed to fluid flow to suit a particular set of fluid system conditions.
These and other objects, features, and advantages of the present invention will be understood from the following detailed description.